Advancing Scalable Quantum Computing: Quantum Dots and Photonic Strategies
Shannon Harvey, a scientist at the U.S. Department of Energy’s (DOE) SLAC National Accelerator Laboratory, is developing scalable quantum dot qubits. This work is conducted as part of Q-NEXT, a DOE National Quantum Information Science Research Center led by Argonne National Laboratory in partnership with SLAC. The research focuses on designing silicon-based quantum dots that can be manufactured at scale, addressing fundamental challenges such as noise and qubit control to create a pathway toward building larger quantum processors using semiconductor-compatible approaches.
The Mechanics of Quantum Dots
At the SLAC National Accelerator Laboratory—a national basic research laboratory devoted to experimental and theoretical research in elementary particle physics and the development of new techniques in high-energy accelerators—researchers are exploring the potential of quantum dots. These are zero-dimensional particles that act as qubits. By confining an electron in a space smaller than its own wavelength, the particle is forced to take on a set of specific energy values. This confinement transforms the electron’s wave into a series of distinct wavelengths, allowing scientists to fine-tune how the electron stores and shares information.
For Shannon Harvey, the appeal of this work lies in the ability to manipulate nature’s quantum features using contemporary technology. “What I love about working in quantum information is that we can use today’s technologies to play with nature’s quantum features, something that until recently would have seemed incredible,” Harvey said. She emphasizes that the primary advantage of this qubit species is its tunability and potential for mass production. “The real selling point of quantum dot qubits is that they’re scalable,” Harvey noted. “You can put a ton of them on a chip and then build a quantum computer on that chip.”
Research at Q-NEXT involves a highly interdisciplinary approach. Harvey describes the day-to-day reality of this scientific endeavor as requiring both mental and manual dexterity. “I really thrive on the multifaceted nature of this research, solving and coming up with problems by embedding myself in the experimental details and trying to understand how they all fit together,” she explained. “For me, scientific exploration involves reading and writing papers, solving math problems, even soldering and welding. Often within the same day.”
The Photonic Quantum Computing Landscape
While SLAC focuses on matter-based qubits, the broader quantum industry is simultaneously advancing photonic quantum computing. This approach encodes information in individual particles of light rather than superconducting circuits or trapped ions. Photonic systems offer distinct advantages, including the ability to operate at room temperature—avoiding the need for costly dilution refrigerators—and natural compatibility with existing fiber optic telecommunications infrastructure.
The global photonic landscape is currently led by several key companies pursuing diverse architectural strategies:
- PsiQuantum (United States): Founded in 2016 and headquartered in Palo Alto, California, the company is developing fault-tolerant photonic quantum computers using standard semiconductor fabrication processes. PsiQuantum has raised over $2 billion in total funding, including a $1 billion Series E round completed in September 2025. The company is currently building deployment sites in Chicago and Brisbane, Australia, the latter supported by $940 million in government backing. It maintains a partnership with GlobalFoundries for chip production.
- Xanadu (Canada): Established in 2017 in Toronto, Xanadu has raised over $287 million. The company utilizes squeezed light for its photonic quantum processors and has demonstrated quantum computational advantage through Gaussian boson sampling experiments. In 2025, Xanadu achieved a technical milestone regarding GKP (Gottesman-Kitaev-Preskill) states for error correction, and in early 2026, the company announced plans to go public.
- Quandela (France): Founded in 2017 and based in Palaiseau near Paris, Quandela specializes in single-photon sources. Having raised over $71 million, the company has delivered systems to major institutions, including the French Alternative Energies and Atomic Energy Commission (CEA). Its MosaiQ platform allows users to access photonic quantum computers via the cloud, and it continues to develop its BELENOS and CANOPUS systems.
Technical Challenges and Future Outlook
Despite the promise of quantum technologies—which are expected to accelerate drug discovery, enhance financial transaction security, and provide eavesdrop-proof telecommunications—significant technical barriers remain. For photonic systems, companies must overcome hurdles related to photon loss, deterministic photon generation, and efficient detection. Similarly, researchers at SLAC continue to refine the stability of quantum dots, working to ensure these particles can be manufactured at scale while maintaining control over their energy values.
As these research centers and private entities continue their work, the focus remains on building practical, reliable systems. Whether through silicon-based quantum dots or integrated photonic chips, the objective is to move beyond theoretical concepts toward hardware that can support the complex demands of future quantum information science.
Find more reporting in our Technology section.
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